Use failure for Pool and Committed errors (#2570)

It doesn't play nice with failure-based error management, we have to
throw away an exisiting error and create a new one (failure-based)

pool/src/types.rs

@@ -23,6 +23,7 @@ use self::core::core::hash::Hash;
 use self::core::core::transaction::{self, Transaction};
 use self::core::core::{BlockHeader, BlockSums};
 use self::core::{consensus, global};
+use failure::Fail;
 use grin_core as core;
 use grin_keychain as keychain;
 
@@ -179,32 +180,44 @@ pub struct TxSource {
 }
 
 /// Possible errors when interacting with the transaction pool.
-#[derive(Debug)]
+#[derive(Debug, Fail)]
 pub enum PoolError {
 	/// An invalid pool entry caused by underlying tx validation error
+	#[fail(display = "Invalid Tx {}", _0)]
 	InvalidTx(transaction::Error),
 	/// An invalid pool entry caused by underlying block validation error
+	#[fail(display = "Invalid Block {}", _0)]
 	InvalidBlock(block::Error),
 	/// Underlying keychain error.
+	#[fail(display = "Keychain error {}", _0)]
 	Keychain(keychain::Error),
 	/// Underlying "committed" error.
+	#[fail(display = "Committed error {}", _0)]
 	Committed(committed::Error),
 	/// Attempt to add a transaction to the pool with lock_height
 	/// greater than height of current block
+	#[fail(display = "Immature transaction")]
 	ImmatureTransaction,
 	/// Attempt to spend a coinbase output before it has sufficiently matured.
+	#[fail(display = "Immature coinbase")]
 	ImmatureCoinbase,
 	/// Problem propagating a stem tx to the next Dandelion relay node.
+	#[fail(display = "Dandelion error")]
 	DandelionError,
 	/// Transaction pool is over capacity, can't accept more transactions
+	#[fail(display = "Over capacity")]
 	OverCapacity,
 	/// Transaction fee is too low given its weight
+	#[fail(display = "Low fee transaction {}", _0)]
 	LowFeeTransaction(u64),
 	/// Attempt to add a duplicate output to the pool.
+	#[fail(display = "Duplicate commitment")]
 	DuplicateCommitment,
 	/// Attempt to add a duplicate tx to the pool.
+	#[fail(display = "Duplicate tx")]
 	DuplicateTx,
 	/// Other kinds of error (not yet pulled out into meaningful errors).
+	#[fail(display = "General pool error {}", _0)]
 	Other(String),
 }